The winding of webs of film onto rolls is an important industrial operation because many commonly used film materials, such as magnetic recording tape, would become impractical if they could not be stored and transported in roll form. Complete use of the advantages inherent in the roll form of tape storage requires that certain conditions of tape winding be met. During winding, each wrap, or strand, of magnetic recording tape wound onto the roll must be precisely aligned to be accurately superimposed over the previously wound strand. If a strand is misaligned, one of its edges can protrude beyond the edge of the overall roll, thereby leaving it unprotected and subject to damage during handling. Moreover, rolls of tape having unaligned strands have an unsightly appearance due to the roughness of the sides of the roll formed by misaligned edges of the strands. Also, the winding speed must be sufficiently low to prevent excessive vibration of the roll because vibration causes misaligned strands. This imposes a significant constraint upon productivity, because higher winding speeds are essential to improved productivity. There is a need to provide a way to reduce roll vibration at higher winding speeds.
Two major causes of tape roll vibration during high speed winding are eccentricity and hub wobble. Hub wobble results from axial misalignment, or skew, of the tape roll, relative to the axis of rotation of winding. When the roll of tape is in axial alignment, it rotates in a plane perpendicular to the axis of rotation, with no movement of the outer periphery of the roll in the axial direction. Eccentricity results when the axis of the roll of tape being wound is not coincident, though it may be parallel with, the axis of rotation of winding. Coincidence of the geometric axis of the tape roll with the axis of winding rotation is called radial alignment.
Magnetic recording tape is typically wound onto a circular core, or hub, which is mounted on a rotating mandrel using a holding device typically called a rotary chuck. Typical hubs suitable for winding magnetic tape are disclosed in U.S. Pat. Nos. 3,632,053 and 4,923,137. In achieving radial and axial alignment of tape rolls, it is essential to radially and axially align the hub on which the tape is to be wound.
Radially and axially aligning rotating members which assure rotation parallel to a fixed plane without eccentricity or wobble, are well known. However, known alignment systems can not be readily applied to manufacturing situations, where the rotating members must be quickly installed and aligned without time-consuming adjustment. For example, when the rotating members are hubs for carrying rolls of magnetic tape, production workers must be able to quickly install them radially and axially aligned.
In U.S. Pat. No. 3,934,833, a hub holding system has a shoulder against which hubs can be pressed to help improve alignment. Unfortunately, these aligning shoulders are not retractable, and it appears that during roll changes, virtually the entire mandrel assembly must be disassembled to remove finished rolls and install new hubs. Additionally, it is not clear that the alignment shoulders provide adequate alignment for large diameter rolls of tape, since nothing seats the hubs against the shoulder of the chuck. Further, no mating reference surfaces between the hub and the chuck are specified as suitable for providing adequate hub alignment.
An additional constraint upon the type of hub alignment system which can be used is that it is often necessary to mount several hubs on a single mandrel. U.S. Pat. No. 4,332,356 discloses a system for holding several hubs on a single chuck, but with no system for alignment. Winding devices of this sort are commonly used where a wider web is slit into narrower tapes, as is commonly done in the manufacture of magnetic recording tapes. An important feature of this type of winding apparatus is that all of the hubs be allowed to slide onto the mandrel, and the finished rolls of wound material be quickly removable from the mandrel with a minimum of mechanical disassembly.
There is a need for a rotary chuck for holding a film winding hub in precise radial and axial alignment relative to a rotating mandrel to allow high speed winding without eccentricity effects or hub wobble. There is also a need for a rotary chuck for holding a tape winding hub in precise radial and axial alignment in which several chucks can be installed on a single mandrel for simultaneous winding of several tapes and which is suitable for use in a large scale manufacturing process. There is a need for such a rotary chuck which allows quick and easy installation, with automatic alignment, of the hub onto the chuck, and allows quick and easy removal of wound rolls from the chuck.